Halogen containing organoboron compounds and method of preparation



United States Patent 3,287,416 HALOGEN CONTAINING ORGANOBORON COM- POUNDS AND METHOD OF PREPARATION Jack Bobinski, Rockaway, and Nelson N. Schwartz,

Morristown, N.J., assignors to Thiokol Chemical Corporation, Bristol, Pa., a corporation of Delaware No Drawing. Filed Oct. 21, 1960, Ser. No. 64,216 11 Claims. (Cl. 260-6065) This invention relates to halogen containing organoboron compounds and to a method for their preparation. The halogen containing organoboron compounds are prepared by the reaction of a bis(nitrile) decaborane or a bis(nitrile) alkyldecaborane with a monoor di-halogenated alkyne containing from 2 to carbon atoms. The reaction products prepared by the method of this invention can be either solid or liquid and are useful as fuels.

The preparation of decaborane is known in the art. Lower alkyl decaboranes such as monomethyldecaborane, dimethyldecaborane, monoet-hyldecaborane, diethyldecaborane, monopropyldecaborane and the like can be prepared, for example, according to the method described in application Serial No. 497,407, filed March 28, 1955, now US. Patent No. 2,999,117, by Elmar R. Altwicker, Alfred B. Garrett, Samuel W. Harris and Earl A. Weilmuenster.

The solid products prepared in accordance with the method of this invention, when incorporated with suitable oxidizers such as ammonium perchlorate, potassium perchlorate, sodium perchlorate, ammonium nitrate and thelike, yield solid propellants suitable for rocket power plants and other jet propelled devices. Such propellants burn with high flame speeds, have high heats of combustion and are of the high specific impulse type. The solid products of this invention when incorporated with oxidizers are capable of being formed into a wide variety of grains, tablets, and shapes, all with desirable mechanical and chemical properties. Propellants produced by the methods described in this application burn uniformly without disintegration when ignited by conventional means, such as a pyrotechnic type igniter, and are mechanically strong enough to withstand ordinary handling.

The liquid products of this invention can be used as fuels according to the methoddescri-bed in the above application Serial No. 497,407, now US. Patent No. 2,999,117.

In accordance with this invention, it was discovered that bis(nitrile)decaboranes and bis(nitrile)alkyldecaboranes will react with a halogen containing acetylenic compound containing from 2 to 10 carbon atoms and from 1 to 2 halogen atoms. Such reaction produces compounds of the class wherein R and R' are selected from the class consisting of hydrogen, alkyl radicals and haloalkyl radicals and the total number of carbon atoms in R and R being from 1 to 8, R" is a lower alkyl radical and n varies from 0 to 4.

Bis (nitrile)decaboranes can be prepared by the method described in copending application Serial No. 690,407, filed October 15, 1957, of Murray S. Cohen et a1. Suitable bis (nitrile)decaboranes disclosed in that application include those prepared by reacting 0.01 to 14 moles of a nitrile of an unsubstituted saturated monocarboxylic acid having from 1 to 6 carbon atoms per mole of decaborane at a temperature of 0 to 180 C.

Bis(nitrile)alkyldecaboranes can be prepared by the method described in copending application Serial No.

751,804, filed July 29, 1958 of Edmond L. Graminski' et al. That application discloses the preparation of solid reaction products of a lower alkyl decaborane and an alkyl cyanide by reacting a lower alkyl decaborane with from 1 to 15 moles, per mole of lower alkyl decaborane, of an alkyl cyanide containing from 1 to 4 carbon atoms in the alkyl radical at a temperature of about 50 to 100 C.

Suitable acetylenic compounds include propargyl bromide; propar-gyl iodide, diiodoacetylene; 3-chlorobutyne- 1; 3-bromobutyne-1; 4-bromobutyne-1; 1,4-dichlorobutyne-2; l-bromopentyne-l; 1-chloropentyne-3; l-bromopentyne-3; l-bromohexyne- 1; 2-bromo-2-methylbutyne-3; and the like.

The ratio of reactants can be varied widely, generally being in the range of 0.1 to 1 moles of bis(nitrile)decaborane or bis(nit-rile)alkyldecaborane per mole of acetylenic compound, and preferably in the range of 0.5 to 1 mole of bis(nitrile)decaborane or bis(nitrile)alkyldecaborane per mole of acetylenic compound. The reaction temperature can vary widely, generally being from 25 to 200 C. and preferably between to 110 C. The reaction pressure can vary from subatmospheric to several atmospheres, i.e., from 1 to 20 atmospheres, although atmospheric pressure reactions are convenient. The reaction generally requires about 1 to 48 hours, depending upon the ratio of reactants, the particular reactants and solvents employed and the temperature and pressure of the reaction.

The reaction is conducted in an aromatic hydrocarbon solvent, such as benzene, toluene or xylene, except that where one of the reactants is a liquid, a solvent need not be employed. The amount of solvent can vary widely.

but generally ranges up to about 10 times the weight of the reactants.

The process of the invention is illustrated in detail by the following examples.

Example I Example II Bis(acetonitrile)decaborane, 2 grams (0.01 mole), suspended in milliliters of 1,4-dichloro-2-butyne, was heated to 6065 C. A vigorous reaction occurred leaving a clear brown solution. The solution was concentrated in vacuo leaving a residue from which 9 grams of white crystals were obtained on sublimation. An elemental analysis of the white crystals showed that they contained 29.02% of chlorine and 44.3% boron, indicati'ng an empirical formula of C H B Cl. The molecular weight of the white crystals was determined to be 233 indicating the molecular formula The boron-containing solid materials produced by practicing the methods of this invention can be employed as ingredients of solid propellant compositions in accordance with general procedures which are well understood in the art, inasmuch as the solids produced by practicing the present process are readily oxidized using conventional solid oxidizers such as amonium perchlorate, potassium perchlorate, sodium perchlorate, ammonium nitrate and the like. In formulating a solid propellant composition employing one of the materials produced in accordwith the present invention, generally from 10 to 35 parts by weight of boron containing material and from 65 to 90 parts by weight of the oxidizer are used. In the propellant, the oxidizer and the product of the present process are formulated in intimate admixture with each other, as by finely subdividing each of the materials and thereafter intimately mixing them. The purpose in doing this, as the art is well aware, is to provide proper burning characteristics in the final propellant. In addition to the oxidizer and the oxidizable material, the final propellant can also contain an artificial resin, generally of the ureaformaldehyde or phenol-formaldehyde type. of the resin is to give the propellant mechanical strength and at the same time improve its burning characteristics. Thus, in the manufacture of a suitable propellant, proper proportions of fiinely divided oxidizer and finely divided boron-containing material can be admixed with a high solids content solution of partially condensed urea-formaldehyde or phenol-formaldehyde resin, the proportions being such that the amount of resin is about 5 to percent by weight based upon the weight of the oxidizer and the boron compound. The ingredients can be thoroughly mixed with a simultaneous removal of solvent, and following this the solvent f-ree mixture can be molded into the desired shape as by extrusion. Thereafter the resin can be cured by resorting to heating at moderate temperatures. For further information concerning the formulation of solid propellant compositions, reference is made to U.S. Patent 2,622,277 to Bonnell and to US. Patent 2,646,596 to Thomas.

The liquid compositions of this invention can be employed as fuels when burned with air. Thus, they can be used as fuels in basic and auxiliary combustion systems in gas turbines, particularly aircraft gas turbines of the turbojet or turboprop type. Each of those types is a device in which air is compressed and fuel is then burned in a combustor in admixture with the air. Following this, the products of combustion are expanded through a gas turbine. The products of this invention are particularly suited for use as a fuel in the combustors of aircraft gas turbines of the types described in vie-w of their improved energy content, combustion efiiciency, combustion stability, flame propagation, operational limits and heat release rates over fuels normally used for these applications.

The combustor pressure in a conventional aircraft gas turbine varies from a maximum at static sea level conditions to a minimum at the absolute ceiling of the aircraft which may be 65,000 feet or 70,000 feet or higher. The compression ratios of the current and near-future aircraft gas turbines are generally within the range from 5:1 to or :1, the compression ratio being the absolute pressure of the air after having been compressed (by the compressor in the case of the turbojet or turboprop engine) divided by the absolute pressure of the air before compression. Therefore, the operating combustion pressure in the combustor can vary from approximately 90 to 300 pounds per square inch absolute at static sea level conditions to about 5 to 15 pounds per square inch absolute at the extremely high altitudes of approximately 70,000 feet. The products of this invention are Well adapted for efiicient and stable burning in combustors operating under these widely varying conditions.

In normal aircraft gas turbine practice it is customary to burn the fuel, under normal operating conditions, at overall fuel-air ratios by weight of approximately 0.012 to 0.020 across a combustion system when the fuel employed is a simple hydrocarbon, rather than a borohydrocarbon of the present invention. Excess air is introduced into the combustor for dilution purposes so that the resultant gas temperature at theturbine wheel in the case of the turbojet or turboprpo engine is maintained at the tolerable limit. In the zone of the combustor where the The function a 4 fuel is injected the local fuel-air ratio is approximately stoichiometric. This stoichiometric fuel to air ratio exists only momentarily, since additional air is introduced along the combustor and results in the overall ratio of approximately 0.012 to 0.020 for hydrocarbons before entrance into the turbine section. For the higher energy fuels of the present invention, the local fuel to air ratio in the zone of fuel injection should also be approximately stoichiometric, assuming'that the boron, halogen, carbon and hy-.

drogen present in the products burn to boric oxide, hydrogen halide, carbon dioxide and water vapor. In the case of the for example, this local fuel to air ratio by Weight is approximately 0.081. For the higher energy fuels of the present invention, because of their higher heating values in comparison with the simple hydrocarbons, the overall fuel-air ratio by weight across the combustor will be approximately 0.008 to 0.016 if the resultant gas temperature is to remain within the presently established tolerable temperature limits. Thus, when used as the fuel supplied to the combustor of an aircraft gas turbine engine, the liquid products of the present invention are employed in essentially the same manner as the simple hydrocarbon fuel presently being used. The fuel isinjected into the combustor in such a manner that there is established a local zone where the relative amounts of fuel and air are approximately stoichiometric so that combustion of the fuel can be reliably initiated by means of an electrical spark or some similar means. After this has been done, additional air is introduced into the combustor in order to cool sufficiently the products of combustion before they enter the turbine so that they do not damage the turbine. Present-day turbine blade materials limit the turbine inlet temperature to approximately 1600-1650 F. Operation at these peak temperatures is limited to periods of approximately five minutes at take-off and climb and approximately 15 minutes at combat conditions in the case of military aircraft. By not permitting operation at higher temperatures and by limiting the time of operation at peak temperatures, satisfactory engine life is assured. Under normal cruising conditions for the aircraft, the combustion products are sufiiciently diluted with air so that a temperature of approximately 1400 F. is maintained at the turbine inlet.

The liquid products of this invention can also be employed as aircraft gas turbine fuels in admixture with the hydrocarbons presently being used, such as JP4. When such mixtures are used, the fuel-air ratio in the zone of the combustor where combustion is initiated and the overall fuel-air ratio across the combustor will be proportional to the relative amounts of borohydrocarbon of the present invention and hydrocarbon fuel present in the mixture, and consistent with the air dilution required to maintain the gas temperatures of these mixtures within accepted turbine operating temperatures.

Because of their high chemical reactivity and heating values, the liquid products of this invention can be employed as fuels in ramjet engines and in after-burning and other auxiliary burning schemes for the turbojet and bypass or ducted type engines. The operating conditions of afterburning or auxiliary burning schemes are usually more critical at high altitudes than those of the main gas turbine combustion system because of the reduced pressure of the combustion gases. In all cases the pressure is only slightly in excess of ambient pressure and efiicient and stable combustion under such conditions is normally difficult with simple hydrocarbons. Extinction of the combustion process in the afterburner may also occur under these conditions of extreme altitude operations with conventional aircraft fuels.

The burning characteristics of the liquid products of this invention are such that good combustion performance can be attained even at the marginal operating conditions encountered at high altitudes, insuring eflicient and stable combustion and improvements in the zone of operation before lean and rich extinction of the combustion process is encountered. Significant improvements in the non-afterburning performance of a gas turbineafterburner combination is also possible because the high chemical reactivity of the products of this invention eliminates the need of flameholding devices within the combustion zone of the afterburner. When employed in an afterburner, the fuels of this invention are simply substituted for the hydrocarbon fuels which have been heretofore used and no changes in the manner of operating the afterburner need be made.

The ramjet is also subject to marginal operating conditions which are similar to those encountered by the afterburner. These usually occur at reduced flight speeds and extremely high altitudes. The liquid products of this invention will improve the combustion process of the ramjet in much the same manner as that described for the afterburner because of their improved chemical reactivity over that of simple hydrocarbon fuels. When employed in a ramjet the liquid fuels of this invention will be simply substituted for hydrocarbon fuels and used in the established manner.

We claim:

1. A method for the. production of an organoboron compound useful as a fuel which comprises reacting a borane selected from the group consisting of bis (nitrile)- decaboranes and .b-is(nitrile)alkyldecaboranes with an acetylenic compound selected from the group consisting of monoand dihalogenated alkynes containing from two to ten carbon atoms the bis(nitrile)decaboranes being the reaction products of decaborane with a nitrile of an unsubstituted aliphatic carboxylic acid having from 1 to 6 carbon atoms, and the bis(nitrile)alkyldecaboranes being the reaction products of a lower alkyldecaborane pound is 1,4-dichloro-2-butyne.

7. The method of claim 1 wherein the borane is bis(acetonitrile)decaborane and the acetylenic compound is 1,4-dichloro-2-butyne.

8. The method of claim 2 wherein the borane is bis(acetonitrile)decaborane, the acetylenic compound is propargyl bromide, and the aromatic hydrocarbon solvent is benzene.

9. Compounds of the class wherein R and R are selected from the class consisting of hydrogen, alkyl radicals and haloalkyl radicals and the total number of carbon atoms in R and R being from 1 to 8, R" is a lower alkyl radical and n varies from 0 to 4.

No references cited.

TOBIAS E. LEVOW, Primary Examiner.

LEON D. ROSDOL, Examiner.

L. A. SEBASTIAN, W. F. W. BELLAMY,

Assistant Examiners. 

1. A METHOD FOR THE PRODUCTION OF AN ORGANOBORON COMPOUND USEFUL AS A FUEL WHICH COMPRISES REACTING A BORANE SELECTED FROM THE GROUP CONSISTING OF BIS(NITRILE)DECABORANES AND BIS(NITRILE) ALKYLDECABORANES WITH AN ACETYLENIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF MONO- AND DIHALOGENATED ALKYNES CONTAINING FROM TWO TO TEN CARBON ATOMS THE BIS(NITRILE) DECABORANES BEING THE REACTION PRODUCTS OF DECABORANE WITH A NITRILE OF AN UNSUBSTITUTED ALIPHATIC CARBOXYLIC ACID HAVING FROM 1 TO 6 CARBON ATOMS, AND THE BIS(NITRILE) ALKYLDECABORANES BEING THE REACTION PRODUCTS OF A LOWER ALKYLDECABORANE WITH AN ALKYL CYANIDE CONTAINING FROM 1 TO 4 CARBON ATOMS IN THE ALKYL GROUP.
 9. COMPOUNDS OF THE CLASS 